Prior art infusion pumps and, in particular, those used for medical purposes for infusing relatively small quantities of liquid over a predetermined period of time into a patient's body have typically used stepper motors to drive the pumping mechanism. The main reasons for this appears to relate to the requirement in many infusion situations that the proportion of material delivered per unit of time must be closely regulated. A stepper motor allows regulated metering without the necessity for using feedback circuits. Stepper motors are, however, relatively expensive propulsion devices and can be somewhat inflexible where a wide range of accurately proportioned delivery rates is required in the one infusion device. They are also inefficient and have lower torque output.
Given the preferred use of disposable components in drug delivery systems it is desirable to provide an infusion system which does not contain any invasive components in direct contact with the fluid to be delivered. This might be required if pressure feedback was desired in combination with a stepper motor drive.
It is an object of the present invention to overcome or substantially ameliorate the abovementioned disadvantages whilst utilizing a continuous drive type motive means for the infusion pump.